165 - Volatile Pyrethroids Against Mosquitoes: A meta-analysis of the association between mosquito exposure to volatile pyrethroid-based spatial repellents and mosquito bite prevention

Abstract: In recent years, products using volatile pyrethoirds have been of increasing interest for addressing outdoor-biting Anopheles mosquitoes responsible for malaria transmission, as well as dengue virus and Zika, both of which are untreatable and on the rise due to rapid urbanization. There is a need to harmonize the growing evidence around volatile pyrethroids against mosquitoes, for the existing evidence base is heterogeneous comprising of different active ingredients, prototypes, study methodologies and scenarios, and entomological outcomes. This meta-analysis study (PROSPERO #CRD42021268852) seeks to consolidate this evidence base, summarizing their protective efficacy using human landing catch and/or trap density as primary outcomes. Secondary outcomes include their duration of efficacy, entomological outcomes such as knock-down, delayed mortality, fecundity and oviposition, and diversion. Results are stratified by active ingredient, spatial repellent format, mosquito species affected, indoor vs outdoor studies, field vs semi-field study, and insecticide resistance assessments among field-caught mosquitoes.
We present interim results on this project, including a literature search of 1,145 published abstracts to identify 42 full-text articles eligible for inclusion, and acquisition of the majority of original datasets from these publications. Data synthesis includes the creation of forest plots summarizing the protective efficacy of volatile pyrethroid products and prototypes from each study, as well as preliminary analyses on aggregate data summarizing the overall protective efficacy of various product classes and prototypes separated by the variables described for stratification above, with separate plots for each entomological outcomes on post-exposure effects where data are available. Sensitivity analysis investigates the impact of temperature and relative humidity on their duration of efficacy, drawing upon satellite data as necessary. Results are expected to be useful for parametrizing disease transmission models, and to determine settings and use cases where these products can most effectively reduce disease transmission.